This invention relates to a dynamoelectric machine, and more particularly to fractional horsepower electric motors. Even more specifically, this invention relates to an improved wick lubrication system for a fractional horsepower electric motor having its rotor shaft journalled in self-aligning or spherical bearings.
Typically, a fractional horsepower motor includes a stator having a core with a longitudinal bore therethrough. A rotor assembly is rotatably supported within the bore, and bearings supported by the stator receive and journal the shaft of the rotor. Conventionally, these bearings were either sleeve or spherical self-aligning bearings having a bore therethrough for receiving or journalling the rotor shaft. Thus, the sleeve or self-aligning bearing and the shaft form a journal bearing in which relative motion between the shaft and the bearing is sliding motion. Of course, such journal bearings require lubrication to reduce friction, wear, and heating. Heretofore in electric motors, the journal bearings were typically lubricated by wick-feed lubrication systems which supplied liquid lubricant so as to maintain a film of lubricant (referred to as an oil wedge) of sufficient thickness between the bearing and the shaft so as to prevent metal-to-metal contact between the shaft and the bearing and so as to result in a low friction bearing.
Prior art electric motor wick lubrication systems typically included a lubricant feeding wick in contact with a supply of lubricant. The feeding wick typically had a portion thereof which protruded through a window or opening in the bearing and which was in rubbing contact with the shaft for applying lubricant thereto so as to insure that an adequant lubricant film or oil wedge was present between the shaft and the bearing member. Oftentimes, as shown in FIG. 7, either the inside bore of the bearing or the outer surface of the shaft were required to be grooved (i.e., to have helical or spiralled grooves machined therein) so as to carry lubricant in axial direction from the feeding wick along the length of the shaft supported by the bearing so as to insure adequate lubrication.
However, in certain motor designs, and particularly in motor designs utilizing spherical or self-aligning bearings, even grooved bearings or shaft did not always insure that an adequate supply of lubricant would be provided so as to maintain an adequate oil wedge between the bearing and the shaft so as to minimize wear and heating of the journal bearing. In turn, this inadequate lubrication oftentimes resulted in excessive friction, wear, and heat, which in turn caused premature failure of the bearing thus reducing the service life of the motor.
Reference may be made to U.S. Pat. No. 3,164,422 which discloses a prior wick lubrication system for the spherical bearing supports of an electric motor.
Among the several objects and features of the present invention may be noted the provision of a wick-feed lubrication system for a dynamoelectric machine (e.g., a fractional horsepower motor) which supplies adequate lubricant to the shaft throughout the entire length of the shaft journalled within the bearing without the necessity of grooving either the shaft or the bearing;
The provision of such a lubrication system in which both the radial and thrust bearing surface of an electric motor bearing are adequately lubricated by a single feeding wick;
The provision of such a lubrication system in which the feeding wick is positively secured in place in lubricant applying contact with the shaft; and
The provision of such a lubrication system which is of simple and economical construction, which is easy to install, and which is reliable in operation.
Other objects and features of this invention will be in part apparent and in part pointed out hereinafter.